Electrical properties of intestinal muscle as measured intracellularly and extracellularly

Abstract
Slow waves recorded extracellularly by wicks in air or by implanted wires in vivo were positive, like those recorded intracellularly by pressure or microelectrodes; wicks recorded negative slow waves in volume conditions. Unlike slow waves, spikes reversed polarity between inside and outside in air or implantation. Slow-wave amplitude was maximal in middle of muscularis. Failure of polarity reversal may be due to pressure effects of wick or implanted wire, also to source-sink relations within fields of synchronous activity. Resistance of longitudinal muscle fibers was 52 megohms, of quiescent circular fibers 68 megohms, and of circular fibers showing induced slow waves 58 megohms. Resistance between adjacent longitudinal fibers was 16 megohms, specific protoplasmic resistance was 222 ohms cm. Time constant with intracellular electrodes in a bridge circuit was 10 msec for longitudinal fibers, 21 msec for circular fibers. With extracellular or pressure electrode stimulation, time constants were 52-105 msec for longitudinal fibers. Space constants measured with extracellular stimulation were 1-1.5 mm, whereas those calculated for intracellular stimulation were 118jx. With paired intracellular electrodes of 7-70 fi, separation electrontonic coupling was 70-80%, at wider separations it approached zero. The effective conducting unit appears to be a bundle rather than a chain of single cells.

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